$(function(){
  // console.log('hello world!');
  let $btn = $('input'),
    num = localStorage.getItem('num') || 0;
    $btn.val(`被按了${num}次`);

    $btn.click(()=>{
      localStorage.setItem('num',++num);
      $btn.val(`被按了${num}次`);
    });
});
